Etch profile control of gate contact opening

A device, comprising:

• a first gate structure and a second gate structure over a substrate;
• source/drain regions at opposite sides of the first gate structure;
• source/drain contacts over the source/drain regions, respectively;
• a gate dielectric cap over the first gate structure and having opposite sidewalls interfacing the source/drain contacts;
• an etch-resistant layer over the gate dielectric cap, wherein a bottom surface of the etch-resistant layer is in contact with a top surface of one of the source/drain contacts;
• an etch stop layer over the etch-resistant layer, the etch stop layer having a thickness greater than a thickness of the etch-resistant layer;
• an interlayer dielectric (ILD) layer over the etch stop layer;
• a first gate contact over the first gate structure, the first gate contact extending through the ILD layer, the etch stop layer, and the etch-resistant layer to electrically connect with the first gate structure, wherein a sidewall of the first gate contact has a slope change, along a downward direction, from a vertical shape to a tapered shape at an interface formed by the etch-resistant layer and the gate dielectric cap;
• and
• a second gate contact over the second gate structure, wherein a width at a top surface of the second gate contact is greater than a width at a top surface of the first gate contact.

A device, comprising:

• a first channel region and a second channel region over a substrate;
• a first gate structure over the first channel region;
• a second gate structure over the second channel region;
• a first dielectric cap over the first gate structure;
• a second dielectric cap over the second gate structure;
• a nitride-based etch stop layer over the first dielectric cap and the second dielectric cap;
• an oxide-based etch-resistant layer spacing apart the nitride-based etch stop layer from the first dielectric cap and the second dielectric cap;
• a first gate contact over the first gate structure, the first gate contact extending through the nitride-based etch stop layer, the oxide-based etch-resistant layer, and the first dielectric cap;
• a second gate contact over the second gate structure, the second gate contact extending through the nitride-based etch stop layer, the oxide-based etch-resistant layer, and the second dielectric cap, wherein a width difference between the first and second gate contact is greater than a width difference between the first and second gate structures, wherein a width at a top surface of the second gate contact is greater than a width at a top surface of the first gate contact;
• source/drain regions at opposite sides of the first gate structure;
• and
• source/drain contact over the source/drain regions, respectively, wherein a top surface of the source/drain contact is in contact with a bottom surface of the oxide-based etch-resistant layer.